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The systematic position of Lanthanotus and the affinities of the anguinomorphan lizards
... Lanthanotus borneensis, generally considered to be the sister taxon to Varanus, has labio-lingually compressed teeth with an expanded base, sharp apex, and recurvature [30]. The premaxillary teeth are smaller medially and increase in size laterally towards the maxillary teeth, with the first maxillary tooth being the same height as the last premaxillary tooth (Fig 8E). ...
... In the helodermatid Heloderma suspectum, teeth are conical, sharply pointed, with recurvature. For both the maxilla and dentary, the teeth are smaller in tooth height anteriorly, increase in the middle, and decrease in tooth height posteriorly [30]. The majority of the premaxillary teeth are similar in size, with a slight increase in height observed for the last tooth (Fig 8F). ...
... Shinisaurus crocodilurus has conical teeth with slight narrowing towards the tooth apex, with no recurvature [30]. The dentary and maxillary teeth appear similar in height, except for the first few teeth being slightly smaller. ...
Dental developmental and replacement patterns in extinct amniotes have attracted a lot of attention. Notable among these are Paleozoic predatory synapsids, but also Mesozoic theropod dinosaurs, well known for having true ziphodonty, strongly serrated carinae with dentine cores within an enamel cap. The Komodo dragon, Varanus komodoensis, is the only extant terrestrial vertebrate to exhibit true ziphodonty, making it an ideal model organism for gaining new insights into the life history and feeding behaviours of theropod dinosaurs and early synapsids. We undertook a comparative dental histological analysis of this extant apex predator in combination with computed tomography of intact skulls. This study allowed us to reconstruct the dental morphology, ontogeny, and replacement patterns in the largest living lizard with known feeding behaviour, and apply our findings to extinct taxa where the behaviour is largely unknown. We discovered through computed tomography that V. komodoensis maintains up to five replacement teeth per tooth position, while histological analysis showed an exceptionally rapid formation of new teeth, every 40 days. Additionally, a dramatic ontogenetic shift in the dental morphology of V. komodoensis was also discovered, likely related to changes in feeding preferences and habitat. The juveniles have fewer dental specializations, lack true ziphodonty, are arboreal and feed mostly on insects, whereas the adults have strongly developed ziphodonty and are terrestrial apex predators with defleshing feeding behaviour. In addition, we found evidence that the ziphodont teeth of V. komodoensis have true ampullae (interdental folds for strengthening the serrations), similar to those found only in theropod dinosaurs. Comparisons with other species of Varanus and successive outgroup taxa reveal a complex pattern of dental features and adaptations, including the evolution of snake-like tongue flicking used for foraging for prey. However, only the Komodo dragon exhibits this remarkable set of dental innovations and specializations among squamates.
... The prefrontal and postorbitofrontal facets closely approach one another, being separated by a gap ( Figure 5A: F.gap) comparable in magnitude to that seen in UALVP 59503 and the Cenozoic helodermatid Lowesaurus matthewi [18]. By comparison, the prefrontal and postorbitofrontal have extensive sutural contact in Heloderma and a slight contact in E. mongoliensis, whereas the prefrontal and postfrontal are widely separated in G. pulchrum [5,17,18,22,44]. The posterior margin of the frontal is sinuous, as in UALVP 59503. ...
... Adjacent osteoderms are separated by distinct grooves, as in the helodermatids Heloderma and Lo. matthewi [18,20,44,46], but in contrast to the condition in UALVP 59503. The osteoderms broadly resemble those of UALVP 59503, and differ from those of Heloderma [20,44], in being variably polygonal rather than uniformly hexagonal. ...
... matthewi [18,20,44,46], but in contrast to the condition in UALVP 59503. The osteoderms broadly resemble those of UALVP 59503, and differ from those of Heloderma [20,44], in being variably polygonal rather than uniformly hexagonal. ...
Reported lizard material from the Wapiti Formation (central-western Alberta, Canada) is limited to fragmentary remains of Kleskunsaurus grandeprairiensis and Socognathus unicuspis, a partial dentary attributed to Chamops cf. C. segnis, and a vertebra reportedly comparable to those of the much larger lizard Palaeosaniwa canadensis. P. canadensis is a Late Cretaceous North American member of Monstersauria, a Mesozoic and Cenozoic anguimorph group represented today by five species of Heloderma. Here, we document new squamate material from the DC Bonebed locality (Wapiti Unit 3; Campanian), including a right frontal identified as cf. P. canadensis and a taxonomically indeterminate squamate astragalocalcaneum. A partial skeleton from the Two Medicine Formation of Montana provisionally attributed to P. canadensis has a frontal resembling the corresponding element from the DC Bonebed in overall shape, in having narrowly separated facets for the prefrontal and postorbitofrontal, and in bearing osteoderms similar to the DC specimen’s in ornamentation and configuration. The Two Medicine and DC specimens differ from a roughly contemporaneous frontal from southern Alberta referred to the monstersaur Labrodioctes montanensis. The DC specimen confirms the presence of monstersaurian squamates in the Wapiti Formation, representing the northernmost record of any definitive Late Cretaceous monstersaur to date.
... Although there have been recent alterations to phylogenetic conceptions that have been stable for decades (e.g., Burbrink et al., 2020;Pyron et al., 2013) and the position of Diploglossidae is still debated (as a subclade of Anguidae, Conrad 2008;Gauthier et al., 2012;Pyron et al., 2013; as a distinct clade outside of Anguidae, Burbrink et al., 2020;Zheng & Wiens, 2016), aside from Anguinae three other extant clades were traditionally included in Anguidae. These are Gerrhonotinae, Anniellinae, and the extinct Glyptosaurinae (sensu McDowell & Bogert, 1954; see Gauthier et al., 2012;Sullivan, 1979Sullivan, , 2019note, however, that if Diploglossidae is treated at the family level, then Glyptosaurinae must also be returned to the family level originally proposed by Marsh, 1872, as members of this clade are much more morphologically distinct compared with Anguinae, see below). Glyptosaurinae (sensu McDowell & Bogert, 1954) inhabited North America, Europe, and Asia and are known from the Cretaceous to the late Paleogene-Oligocene (Černǎnský & Augé, 2019;Conrad & Norell, 2008;Keller, 2009;Sullivan, 1979Sullivan, , 2019. ...
... Taxonomic Note-If most clades previously considered subfamilies of Anguidae sensu Camp, 1923-viz., Anguinae, Anniellinae, and Diplglossinae-are now considered taxa at the family level, and there is no evidence that glyptosaurs are part of any of those radiations, then Glyptosaurinae sensu McDowell & Bogert, 1954 must also be returned to the family level originally proposed by Marsh (1872). Accordingly, we consider Glyptosauridae Marsh, 1872 to contain the subfamilies Melanosaurinae Sulli- van, 1979, which is paraphyletic, and Glyptosaurinae Marsh, 1872, which correspond to the tribes Melanosaurini and Glyptosaurini of Sullivan (1979). ...
... Accordingly, we consider Glyptosauridae Marsh, 1872 to contain the subfamilies Melanosaurinae Sulli- van, 1979, which is paraphyletic, and Glyptosaurinae Marsh, 1872, which correspond to the tribes Melanosaurini and Glyptosaurini of Sullivan (1979). The name "Placosauridae" (e.g., Cope, 1877;Kuhn, 1940) is a junior synonym of Glyptosauridae (Estes, 1983;McDowell & Bogert, 1954), so it does not affect our new status. ...
Squamate faunas from the lower Eocene of Europe are rare. A newly discovered lower Eocene (MP 10–11)
Cos locality in southwestern France has yielded an assemblage of anguimorph lizards that sheds light on the early evolution of
this group. Among them is a new glyptosaurine lizard Sullivania gallica gen. et sp. nov., based on frontal material with a unique
pattern and distribution of polygonal osteoderms that is distinct from that of the middle and late Eocene Placosaurus from
France. It slightly resembles the stratigraphically older glyptosaurine Gaultia silvaticus from the earliest Eocene of North
America, but differs from it in several aspects. Although fossils of some members of Glyptosaurinae (sensu this paper;
Glyptosaurini in previous taxonomies—Glyptosaurinae is returned to the family level originally proposed by Marsh) have
been documented rarely from the middle and mainly from the late Eocene of Europe, they are virtually unknown from
the lower Eocene. One isolated osteoderm is referred only to Anguioidea indet. This specimen resembles osteoderms
seen in Anguinae, provided that the absence of tuberclulate ornamentation is not caused by abrasion. Varanoids are
represented by an isolated frontal referred to Palaeovaranidae indet. It possesses a complex ornamentation composed of
mounds on the dorsal surface. A maxilla is identified as an indeterminate varanoid based on the plicidentine infolding
along the bases of the preserved teeth. Although incomplete, this Cos lizard assemblage is an important and rare
discovery that provides a glimpse into the ecosystems and paleobiodiversity of the lower Eocene in western Europe.
... Nopcsa (1923a, b) placed Archaeophis into his Cholophidia, along with certain Cretaceous hind-limbed snakes and the Paleogene palaeophiids, however, in his later works, the same author excluded Archaeophis from that group and instead placed it within alethinophidians (Nopcsa, 1925(Nopcsa, , 1928. McDowell & Bogert (1954) casted some doubt on the true serpent nature of the Italian taxon, suggesting instead that some anatomical features were indicative of a fish and not a snake. This misconception was later clarified by Auffenberg (1959), who attributed McDowell & Bogert's (1954) opinion to a misinterpretation of Janensch's (1906) drawing, and confirmed the ophidian status of Ar. proavus, while also removing Ar. bolcensis from Archaeophis and placing it in its own genus (see below). ...
... McDowell & Bogert (1954) casted some doubt on the true serpent nature of the Italian taxon, suggesting instead that some anatomical features were indicative of a fish and not a snake. This misconception was later clarified by Auffenberg (1959), who attributed McDowell & Bogert's (1954) opinion to a misinterpretation of Janensch's (1906) drawing, and confirmed the ophidian status of Ar. proavus, while also removing Ar. bolcensis from Archaeophis and placing it in its own genus (see below). Tatarinov (1963Tatarinov ( , 1988 described a snake from the Eocene of Turkmenistan, which he referred to the Bolca genus (Archaeophis turkmenicus Tatarinov, 1963). ...
... These three slabs represent the holotype (they were treated as syntypes by Rage, 1984) and only known specimen of An. bolcensis; casts of these slabs exist in MGP-PD and MCSNV. The taxon was discussed by Janensch (1906) and McDowell & Bogert (1954), but it was the revision of Auffenberg (1959) which shed important light on its anatomy. Indeed, Auffenberg (1959) highlighted diagnostic features that he felt were distinct enough from other snakes, and therefore, not only he established the new genus Anomalophis to accommodate it, but also a new family, Anomalophiidae (spelled as Anomalophidae in Auffenberg, 1959). ...
The Eocene fossil reptiles from the Bolca Fossil-Lagerstätte (Verona, Italy) have been known in the literature since at least the 1850’ and were the subject of many studies during the second half of the XIX century and the first decades of the XX century. However, with the exception of a few papers, only rare works have been published on the Monte Bolca herpetofauna in recent years, and in many cases knowledge of the anatomy, taxonomy, and proper nomenclature of the Bolca reptiles still remains uncertain. Herein, we reassess the history of the discoveries, the earlier taxonomy and revisions of the crocodilians, turtles, and snakes from Bolca. To date, a total of 13 crocodilian specimens have been described in the literature or are housed in museum collections and remain unpublished. Two of the crocodilian specimens formerly cited and/or described are currently lost. All the fossil crocodilian specimens had originally been referred to two species, Crocodilus vicetinus Lioy, 1865, and Crocodilus bolcensis Sacco, 1895. In this study these identifications are considered invalid, and some specimens are referred to the genera Asiatosuchus, Boverisuchus, Diplocynodon and Hassiacosuchus while assignment at species level is still debatable. The turtles are represented by multiple specimens, which had been referred in the past to several different taxa of pleurodires and trionychids. However, only two species of turtles from Monte Bolca are currently accepted as being valid, both with species epithets dedicated to the renowned Italian palaeontologist Giovanni Capellini (1833-1922): the pleurodire Neochelys capellinii (de Zigno, 1890), which is the type species of its genus, and the trionychid “Trionyx” capellinii Negri, 1892. Both the crocodilians and the turtles had been collected at the Purga di Bolca locality. Only three snake specimens have been described from the Bolca area, representing also the oldest Cenozoic snakes from Italy: Coluber ombonii de Zigno, 1889 from Purga, and the archaeophiine Archaeophis proavus Massalongo, 1859 and anomalophiid Anomalophis bolcensis (Massalongo, 1859) from the Pesciara locality. The affinities of C. ombonii are still not clear, whereas A. proavus and A. bolcensis are considered valid and represent the type species of their genera but also are among the very few representatives of Archaeophiinae and Anomalophiidae respectively. The fossil reptiles from Bolca are housed in public collections in Italy (Turin, Verona, Padua, Rome, Pavia), the United Kingdom (London), USA (Pittsburgh, Cambridge), Germany (Darmstadt, Berlin) and Austria (Vienna).
... R. Soc. B 377: 20210041 border, and the description in McDowell & Bogert [41] implies the same thing. Moreover, this does appear to be the condition in FMNH148589 [42]. ...
... In ventral view, the basisphenoid-basioccipital suture (figure 2b; electronic supplementary material, figure S7A) is an inverted V-shape with a flat vertex, terminating laterally at the apices of the basal tubera. Norell & Gao [46] described the basisphenoid and basioccipital suture in Estesia mongoliensis as strongly arched anteriorly, which is very similar to the 'obtusely angulate suture' noted by McDowell & Bogert [41] in basal anguimorphs, and also present in Heloderma, but different from the straight-line suture in Varanus and Lanthanotus. This suggests that Archaeovaranus retained the primitive state. ...
... They are small simple bulging structures. Palatal teeth are absent in Varanus and Heloderma, but are present in Lanthanotus (single row on pterygoid, variably on palatine, [41]), Ovoo (single palatine row, two pterygoid rows, [14]) and S. ensidens (single continuous row on palatine and pterygoid, [18]). ...
Monitor lizards (genus Varanus ) are today distributed across Asia, Africa and Australasia and represent one of the most recognizable and successful lizard lineages. They include charismatic living species like the Komodo dragon of Indonesia and the even larger extinct Varanus prisca ( Megalania ) of Australia. The fossil record suggests that living varanids had their origins in a diverse assemblage of stem (varaniform) species known from the Late Cretaceous of China and Mongolia. However, determining the biogeographic origins of crown-varanids has proved problematic, with Asia, Africa and Australia each being proposed. The problem is complicated by the fragmentary nature of many attributed specimens, and the fact that the most widely accepted, and most complete, fossil of a stem-varanid, that of Saniwa ensidens , is from North America. In this paper, we describe a well-preserved skull and skeleton of a new genus of stem-varanid from the Eocene of China. Phylogenetic analysis places the new genus as the sister taxon of Varanus, suggesting that the transition from Cretaceous varaniform lizards to Varanus occurred in East Asia before the origin and dispersal of Varanus to other regions. The discovery of the new specimen thus fills an important gap in the fossil record of monitor lizards. The similar lengths of the fore- and hindlimbs in this new taxon are unusual among the total group Varanidae and suggest it may have had a different lifestyle, at least from the contemporaneous North American S. ensidens .
This article is part of the theme issue ‘The impact of Chinese palaeontology on evolutionary research’.
... The homology of the element named herein as prefrontal has been a matter of debate for "Scolecophidia" and Anomalepididae (Dunn, 1941;Dunn and Tihen, 1944;Haas, 1964Haas, , 1968List, 1966;McDowell and Bogert, 1954). However, shape and topographical features observed in Leptotyphlopidae (Rieppel et al., 2009; present study) allows us to corroborate Haas ' (1964, 1968) proposition of homologizing this element to a prefrontal. ...
... An ectopterygoid is absent in all species of Trilepida (Salazar-Valenzuela et al., 2015;Pinto et al., 2015;present study), with its absence being considered as an exclusive feature of Leptotyphlopidae and Typhlopoidea within Serpentes (McDowell, 1974). However, this element has previously been reported for Leptotyphlopidae by McDowell and Bogert (1954;T. dimidiata) and List (1966; Rena maxima) as an element fused to the posterior process of the maxilla, which was later emphasized by McDowell (2008). ...
... As in other Leptotyphlopidae (Kley, 2006;List, 1966;McDowell and Bogert, 1954;Pinto et al., 2015;Rieppel et al., 2009), the mandible is subterminal, short, and suspended from the skull by the quadrates, which are associated with the skull by a series of cartilages, ligaments, and muscles (Kley, 2006;. The absence of a bone connection to the skull seems to suggest translational movements of the quadrate (McDowell, 2008), providing a more efficient underground feeding apparatus. ...
The threadsnakes of the family Leptotyphlopidae have been historically neglected in terms of their natural history, ecology, systematics, and morphology. Given the relevance of morphological data for resolving systematic, evolutionary, and functional issues, we aimed to provide a detailed comparative description of osteology and associated cartilaginous elements for members of the genus Trilepida. Data were obtained through high‐resolution computed tomography images, cleared and stained specimens, and radiography images of a total of 47 specimens and 12 species. Both cranial and axial osteology characters exhibited a relevant degree of intraspecific variation regarding qualitative and quantitative data associated with skull and vertebrae foramina and the shape of bony sutures and processes. The high representativeness of examined species and specimens allows us to provide a comprehensive discussion on the inter‐ and intraspecific osteological variation, as well as a compelling osteological diagnosis for the entire genus. Trilepida spp. differ from all Epictinae by the presence of the following combination of characters: paired nasals, fused supraoccipitals (distinct from parietal, prootics, and otooccipitals), a single (fused) parietal without a dorsal fontanelle, and the basioccipital participating in the foramen magnum (except in Trilepida nicefori). Our results reinforce the need for integration of detailed anatomical traits to usually conserved external morphological data to provide accurate diagnostic features for Epictinae. In addition, new phylogenetic hypotheses or even taxonomic re‐allocations may broadly benefit from these detailed comparative studies.
... Leaving aside the transient associations of Palaeovaranus material with glyptosaurine anguids (Filhol 1877: 488;Lydekker 1888a: 279) and with shinisaurs (Hoffstetter 1954;McDowell & Bogert 1954;Hoffstetter 1955;Haubold 1977), there have historically been two main views on the relationships of Palaeovaranus (for a detailed review, see Georgalis 2017). According to the one view Palaeovaranus is in fact closely related to its namesake, Varanus (Zittel 1887(Zittel -1890Lydekker 1888b: 111;de Stefano 1903;de Fejérváry 1918de Fejérváry , 1935. ...
... Paired longitudinal rows of enlarged, keeled scales on the nape, like those in "Saniwa" feisti, are otherwise only seen in Lanthanotus, among extant anguimorphs, and the species of The anatomy, phylogenetic relationships, and autecology of the carnivorous lizard "Saniwa" feisti COMPTES RENDUS PALEVOL • 2021 • 20 (23) Varanus noted above. Notably, however, a similar morphology is seen in Shinisaurus, although the rows are multiple (McDowell & Bogert 1954), and occasionally more posteriorly in Xenosaurus (Lemos-Espinal et al. 2012). ...
... obs.); a detailed study of that species will be necessary to determine its similarities to Palaeovaranus. McDowell and Bogert (McDowell & Bogert 1954) observed that the osteoderms in the type specimen of "Necrosaurus eucarinatus" Kuhn, 1940 are also non-imbricate. In fact, some osteoderms do very slightly overlap (although not nearly to the extent seen in Anguidae). ...
The evolution and interrelationships of carnivorous squamates (mosasaurs, snakes, monitor lizards, Gila Monsters) are a contentious part of reptile systematics and go to the heart of conflict between morphological and molecular data in inferring evolutionary history. One of the best-preserved fossils in this motley grouping is “Saniwa” feisti Stritzke, 1983, represented by complete skeletons from the early-middle Eocene of Messel, Germany. We re-describe it on the basis of superficial examination, stereoradiography, and high-resolution X-ray computed tomography of new and published specimens. The scalation of the lizard is unique, consisting of small, keeled scales on the head (including a row of enlarged medial supraorbitals) and large, rhomboidal, keeled scales (invested by osteoderms) that covered the rest of the body. Two paired longitudinal rows of enlarged scales ran down the neck. The head was laterally compressed and box-shaped due to the presence of a strong canthal-temporal ridge; the limbs and tail were very long. Notable osteological features include: a toothed, strap-like vomer; septomaxilla with a long posterior process; palpebral with a long posterolateral process; a lacrimal boss and a single lacrimal foramen; a well-developed cultriform process of the parabasisphenoid; two hypoglossal (XII) foramina in addition to the vagus; a lack of resorption pits for replacement teeth; and possibly the presence of more than one wave of developing replacement teeth per locus. There are no osteological modifications suggestive of an intramandibular hinge, but postmortem displacement of the angular-prearticular-surangular complex in multiple specimens suggests that there might have been some degree of mobility in the lower jaw based on soft-tissue modifications. Using phylogenetic analyses on a data-set comprising 473 morphological characters and 46 DNA loci, we infer that a monophyletic Palaeovaranidae Georgalis, 2017, including Eosaniwa Haubold, 1977, lies on the stem of Varanidae Merrem, 1820, basal to various Cretaceous Mongolian taxa. We transfer feisti to the new genus Paranecrosaurus n. gen. Analysis of gut contents reveals only the second known specimen of the cryptozoic lizard Cryptolacerta hassiaca Müller, Hipsley, Head, Kardjilov, Hilger, Wuttke & Reisz, 2011, confirming a diet that was at least partly carnivorous; the preservation of the teeth of C. hassiaca suggests that the gastric physiology of Paranecrosaurus feisti (Stritzke, 1983) n. comb. had high acidity but low enzyme activity. Based on the foregoing and linear discriminant function analysis, we reconstruct P. feisti n. comb., as a powerful, widely roaming, faunivorous-carnivorous stem monitor lizard with a sensitive snout. If the molecular phylogeny of anguimorphs is correct, then many of the features shared by Helodermatidae Gray, 1837 and Varanidae must have arisen convergently, partly associated with diet. In that case, a reconciliation of morphological and molecular data would require the discovery of equally primitive fossils on the helodermatid stem.
... According to the results of detailed anatomical studies, the morphological similarities of earless monitor lizard to extinct mosasaurs were pointed out and it was also considered to be a prototype of a transitional form between lizards and snakes (McDowell et Bogert 1954, Schmidt et Inger 1957, McDowell 1967, Bellairs 1972. At the same time, however, Underwood (1957) critically points to many inconsistencies in the data and interpretations provided by McDowell and Bogert (1954). ...
... According to the results of detailed anatomical studies, the morphological similarities of earless monitor lizard to extinct mosasaurs were pointed out and it was also considered to be a prototype of a transitional form between lizards and snakes (McDowell et Bogert 1954, Schmidt et Inger 1957, McDowell 1967, Bellairs 1972. At the same time, however, Underwood (1957) critically points to many inconsistencies in the data and interpretations provided by McDowell and Bogert (1954). Newer, osteologically based, phylogenetic analyses (e.g. Lee 1997, Rieppel et Zaher 2000 no longer consider Lanthanotus borneensis to be immediately close to ancestral forms in the evolution of snakes and point to their close relationships with monitor lizards. ...
... Podle výsledků detailních anatomických studií bylo upozorněno na morfologické podobnosti varanovců s vymřelými mosasaury a uvažovalo se o nich i jako o prototypu přechodného článku mezi ještěry a hady (McDowell et Bogert 1954, Schmidt et Inger 1957, McDowell 1967, Bellairs 1972. Současně ale Underwood (1957) kriticky poukazuje na mnohé nesrovnalosti v údajích a interpretacích, které podali McDowell et Bogert (1954). ...
Starting in 2014, members of the European Association of Zoos and Aquariums (EAZA) began to acquire earless monitor lizards. In this paper, the focus is on the ex situ population of Lanthanotus borneensis in EAZA, its origin, current status, role and perspectives.
... Even though the skull of Afrotyphlops punctatus has previously been illustrated or shortly described by some authors (Baird, 1970;Dowling & Duellman, 1978;McDowell & Bogert, 1954;Parker & Grandison, 1977;Phisalix, 1914;Radovanovic, 1937;Rieppel, 1979;Zaher & Rieppel, 1999), a detailed description of the skull was only provided by Haas (1930). However, detailed data regarding the skull internal aspects as well as data on the intraspecific variation has not yet been provided in detail. ...
... The genus Afrotyphlops currently contains about 29 recognized species (Uetz et al., 2020) traditionally known as African giant blindsnakes, occurring entirely in sub-Saharan Africa, including satellite islands and islets (Hedges et al., 2014). The species A. punctatus represents the type species of the genus, with its osteology (at least some of its elements) previously depicted or described in the literature (Baird, 1970;Haas, 1930;McDowell & Bogert, 1954;Parker & Grandison, 1977;Phisalix, 1914;Rieppel, 1979;Zaher & Rieppel, 1999). Besides such contributions, as far as we know, only very few additional works have dealt with the osteology of four additional Afrotyphlops species (i.e., A. bibronii, A. blanfordii, A. lineolatus and A. mucruso;Haas, 1930;FitzSimons, 1962;Kley, 2001;List, 1966). ...
... When considering previous papers that have partially described or illustrated the osteology of A. punctatus (Baird, 1970;Haas, 1930;McDowell & Bogert, 1954;Parker & Grandison, 1977;Phisalix, 1914;Rieppel, 1979;Zaher & Rieppel, 1999), we notice that there is no conspicuous variation regarding their morphology, as follows. The maxilla of the specimen analyzed by Zaher & Rieppel (1999) has five teeth, as also found in one of our specimens. ...
Scolecophidians” are traditionally known for their several skull and lower jaw autapomorphies, being conspicuously different from alethinophidian snakes in terms of skull shape and function. Although typically known for the absence of any kinetic joint in the skull dermatocranium and neurocranium—mostly due to an adaptation to fossorial habit, literature data have previously suggested a possible cranial kinesis for individuals of Afrotyphlops punctatus based on observations of live and preserved individuals. Given such observations, herein we aim to describe in detail the skull of A. punctatus based on CT‐scan images of five specimens, evaluating the skull morphology and inferred function, and also providing valuable discussion on the skull osteology of the genus. Our results suggest that the skull of A. punctatus is similar to other blindsnakes in lacking any trace of snout, or even a frontal–parietal articulation. We also discuss possible osteological data that might be systematically relevant for Typhlopidae both interspecifically and intergenerically.
... Fossil lizards from Hall's Cave (Kerr County, Texas) and variation in North American lizard skulls Identification. The fossil shares with many anguimorphs and most scincids co-ossified osteoderms [23], well-developed and ventrally directed cristae cranii (subolfactory processes of [120]), and an unfused frontal [23]. The sculpting on the dorsal surface in scincids is more vermiculate compared to the fossil and to many extant anguimorphs which have a pitted texture, such as Ophisaurus and Elgaria [45] (Fig 39). ...
... There is a postfrontal facet along the posterolateral edge. The ventral portion of the crista cranii (subolfactory processes of [120]) is broken, but the crest is well-developed, tall, and anteroposteriorly long. Ventrally, there is a series of small transverse ridges and corresponding grooves medial to the crista cranii. ...
Fossil identification practices have a profound effect on our interpretation of the past because these identifications form the basis for downstream analyses. Therefore, well-supported fossil identifications are necessary for examining the impact of past environmental changes on populations and communities. Here we apply an apomorphic identification framework in a case study identifying fossil lizard remains from Hall’s Cave, a late Quaternary fossil site located in Central Texas, USA. We present images and descriptions of a broad comparative sample of North American lizard cranial elements and compile new and previously reported apomorphic characters for identifying fossil lizards. Our fossil identifications from Hall’s Cave resulted in a minimum of 11 lizard taxa, including five lizard taxa previously unknown from the site. Most of the identified fossil lizard taxa inhabit the area around Hall’s Cave today, but we reinforce the presence of an extirpated species complex of horned lizard. A main goal of this work is to establish a procedure for making well-supported fossil lizard identifications across North America. The data from this study will assist researchers endeavoring to identify fossil lizards, increasing the potential for novel discoveries related to North American lizards and facilitating more holistic views of ancient faunal assemblages.
... Wyeth 1924;Säve-Söderbergh 1947;Pratt 1948;Evans 2008;Jones 2008), Dibamidae (Rieppel 1984a), and in a limited number of representatives of the higher groups Gekkota (Kluge 1962;Rieppel 1984b;Conrad and Norell 2006;Daza et al. 2008;Bauer et al. 2018), Scinciformata (Rieppel 1981;Paluh and Bauer 2017;Stepanova and Bauer 2021), Laterata (Jollie 1960;Hernández Morales et al. 2018;Holovacs et al. 2019), and Toxicofera (e.g. Säve-Söderbergh 1947;McDowell and Bogert 1954;Oelrich 1956;Rieppel and Zaher 2000;Bever et al. 2005;Conrad and Norell 2008;Cundall and Irish 2008;Conrad and Daza 2015;Paluh and Bauer 2017). Within that latter group, special attention was traditionally given to the highly specialized braincase of snakes (Rieppel 1979a, b;Zaher et al. 2009Zaher et al. , 2022aOlori 2010;Olori and Bell 2012;Yi and Norell 2015;Garberoglio et al. 2019), while broader detailed comparative studies among squamates remain sparse (e.g. ...
... This revision, however, is not intended to be exhaustive, as some early reviews have done a more detailed evaluation of the skull of lepidosaurs (e.g. McDowell and Bogert 1954;Estes 1983;Cundall and Irish 2008;Evans 2008). Instead, an overview of the osteological and neuroanatomical characters that are diagnosable on both fossil and extant groups is presented, showing the relationship between the soft tissues and the endocranial cavity. ...
Braincase descriptions of lepidosaurian clades (Rhynchocephalia and Squamata) are scarce, and paleoneurological studies are even scarcer when compared to other reptiles. Regarding paleoneurology sensu stricto, so far mosasauroids and snakes (the latter by means of a single published study) remain the better known lepidosaur groups. Further comparisons among extinct and living lepidosaurs – along with their evolutive history starting in the early Triassic– are not possible due to the lack of neuroanatomical information in most families. Here we provide a revision of the published literature on endocranial anatomy and paleoneurology in Lepidosauria, including an overview of the comparative braincase and neuroanatomy of living representatives of the clade. We hope that this information will have an impact on future studies in the field of comparative neuroanatomy in both living and extinct species. Micro-CT and diceCT data are currently facilitating neuroanatomical comparisons among living species, preparing the background for a potential rise of paleoneurological studies of non-marine extinct lepidosaurs.
... Snakes were traditionally considered to be close relatives of platynotan anguimorphs (Camp, 1923;McDowell & Bogert, 1954), but recent molecular studies have recovered them in a clade with anguimorphs and iguanians (Toxicofera; Vidal & Hedges, 2005). An analysis by Reeder et al. (2015), which used a morphological and molecular dataset combining the matrices from Gauthier et al. (2012) and Wiens et al. (2012), found six unambiguous morphological synapomorphies supporting Toxicofera. ...
... In the remaining anomalepidid genus, Anomalepis Jan, 1860, the 'postorbital element' extends further posteriorly along the lateral surface of the anterior portion of the parietal (Haas, 1968). This element has been identified variously as a postorbital (Haas, 1964(Haas, , 1968McDowell, 1987), a jugal (Haas, 1962;McDowell, 2008;, a fused postorbitofrontal (Dunn, 1941) and a fused postorbital and jugal (McDowell & Bogert, 1954;List, 1966). Its association with the adductor mandibulae externus superficialis muscle favours the homology with the postorbital, whereas its position on the ventral orbit is consistent with a jugal. ...
Recent phylogenetic analyses differ in their interpretations of the origin and interrelationships of snakes, resulting in polarized views of snake ecology, habit and acquisition of features associated with wide-gaped feeding (macrostomy). Here, we report a new specimen of the Late Cretaceous nest predator Sanajeh indicus that helps to resolve the origin of macrostomy. The new specimen preserves an ossified upper temporal bar and a posteriorly expanded otooccipital region that lacks a free-ending supratemporal bone and retains a lizard-like palatomaxillary arch that allows limited movements during swallowing. Phylogenetic analyses of a large-scale total evidence dataset resolve Sanajeh near the base of Pan-Serpentes, as the sister group of Najash, Dinilysia and crown-group Serpentes. The Cretaceous Tetrapodophis and Coniophis represent the earliest-diverging members of Pan-Serpentes. The Cretaceous hindlimbed pachyophiids and Cenozoic Australian 'madtsoiids' are inside crown Alethinophidia, whereas mosasaurs are recovered invariably within anguimorphs. Our results suggest that the wide-gape condition in mosasaurs and snakes might have evolved independently, as functionally distinct mechanisms of prey ingestion. The intermediate morphology preserved in Sanajeh indicates that ingestion of large prey items (macrophagy) preceded wide-gaped, unilateral feeding (macrostomy), which appeared 35 Myr later, in the common ancestor of pachyophiids, Cenozoic Australian 'madtsoiids' and alethinophidians.
... On the dorsal surface, the ascending process projects anterodorsally and rises at a relatively low angle with respect to the bone. A tall medial crest (sagittal crest of McDowell and Bogert [66]) continues posteriorly on the dorsal surface (Fig. 11a). The base of the ascending process connects to the body of the supraoccipital close to the level of anterior extent of the anterolateral tips of the bone. ...
... Remarks. The frontals of gerrhonotines were previously characterized as 'hour-glass' shaped due to constriction between the orbits [28,66]. Interorbital constriction relative to both the anterior and posterior sections of the bone is present in gerrhonotines as previously reported, but we note that marked interorbital constriction occurs in members of many squamate clades, including varanids, xenosaurids, iguanians, and scincomorphs [19]. ...
Background
Alligator lizards (Gerrhonotinae) are a well-known group of extant North American lizard. Although many fossils were previously referred to Gerrhonotinae, most of those fossils are isolated and fragmentary cranial elements that could not be placed in a precise phylogenetic context, and only a handful of known fossils are articulated skulls. The fossil record has provided limited information on the biogeography and phylogeny of Gerrhonotinae.
Results
We redescribe a nearly complete articulated fossil skull from the Pliocene sediments of the Anza-Borrego Desert in southern California, and refer the specimen to the alligator lizard genus Elgaria . The fossil is a representative of a newly described species, Elgaria peludoverde . We created a morphological matrix to assess the phylogeny of alligator lizards and facilitate identifications of fossil gerrhonotines. The matrix contains a considerably expanded taxonomic sample relative to previous morphological studies of gerrhonotines, and we sampled two specimens for many species to partially account for intraspecific variation. Specimen-based phylogenetic analyses of our dataset using Bayesian inference and parsimony inferred that Elgaria peludoverde is part of crown Elgaria . The new species is potentially related to the extant species Elgaria kingii and Elgaria paucicarinata , but that relationship was not strongly supported, probably because of extensive variation among Elgaria . We explored several alternative biogeographic scenarios implied by the geographic and temporal occurrence of the new species and its potential phylogenetic placements.
Conclusions
Elgaria peludoverde is the first described extinct species of Elgaria and provides new information on the biogeographic history and diversification of Elgaria . Our research expands the understanding of phylogenetic relationships and biogeography of alligator lizards and strengthens the foundation of future investigations. The osteological data and phylogenetic matrix that we provided will be critical for future efforts to place fossil gerrhonotines. Despite limited intraspecific sampled sizes, we encountered substantial variation among gerrhonotines, demonstrating the value of exploring patterns of variation for morphological phylogenetics and for the phylogenetic placement of fossils. Future osteological investigations on the species we examined and on species we did not examine will continue to augment our knowledge of patterns of variation in alligator lizards and aid in phylogenetics and fossil placement.
... Conflicting characters that are often cited as anguimorphan synapomorphies are clearly absent in the dentary from Montchenot: tooth apex pointed and tooth replacement alternate or distally displaced replacement pit on tooth bases (McDowell & Bogert (1954). Pointed, canine like teeth indicative of predaceous habits are common in anguimorph lizards but rounded tooth apex occasionally provided with Varanus, Lanthanotus, Heloderma, Saniwa, Palaeovaranus (Ex Necrosaurus). ...
... Georgalis (2017) pointed out that the name Necrosaurus, as established by Filhol (1876) is a nomina nuda and that Zittel (1887-1890) was the first author to make the name Palaeovaranus cayluxi available. The phylogenetic affinities of Palaeovaranus are a moot point: briefly,McDowell & Bogert (1954) noted significant morphological differences between Palaeovaranus and members of the Platynota (sensuPregill et al. 1986) and they referred it to xenosaurid lizards, an option first adopted by Hoffstetter(1954). Later this author returned Palaeovaranus to the Platynota (Hoffstetter 1962b).Lee (1997) rejected this taxon as paraphyletic. ...
Here we describe the lizard fauna from the locality of Montchenot (Paris Basin, late Paleocene, MP6). This material can be allocated to five major clades: Scincoidea, Lacertoidea (?Lacertidae), Amphisbaenia, Anguimorpha (?Anguidae and Shinisauridae). The assemblage from Monchenot is dominated by small lizard specimens and appears as highly sorted. Predation could produce such biased assemblages. The composition of the lizard fauna from Monchenot is rather similar to those of Cernay-lès-Reims and Rivecourt, two coeval localities (MP6) in the Paris Basin. However, these faunas sharply contrast (in diversity and composition) with the lizard fauna found in the early Eocene of the same area (Paris Basin and Belgian Basin). These differences highlight the impact of the Paleocene/Eocene transition on the lizard fauna of Europe.
... Crown gerrhonotines are known from at least the middle Miocene (Scarpetta, 2018). The osteology of the group was previously studied by several researchers (Cope, 1892;Tihen, 1949;McDowell & Bogert, 1954;Romer, 1956;Criley, 1968;Meszoely, 1970;Rieppel, 1980;Gauthier, 1982;Good, 1987;Good, 1988a); however, only a few species from each group within Gerrhonotinae were sampled. Variation in gerrhonotine osteology was previously reported in studies of ontogenetic variation (Good, 1995) and timing of fusion relative to sexual maturity (Maisano, 2002) in Elgaria coerulea, and an osteological description of the skull of Elgaria panamintina (Ledesma & Scarpetta, 2018). ...
... Lack of fusion between the surangular and articular (including the prearticular) was reported as an unambiguous synapomorphy of anguines, anniellines, gerrhonotines, and glyptosaurines (Conrad et al., 2011), but one researcher reported fusion of the articular and surangular in some gerrhonotines (Criley, 1968). Other authors noted that the bones are fused in most anguid genera (McDowell & Bogert, 1954) or reported that they were not fused (Rieppel, 1980). The surangular and articular are unfused in several specimens of Elgaria and Gerrhonotus. ...
Background
There are limited data on intra- and interspecific osteological variation for many squamate clades. Those data are relevant for phylogenetic analyses that use osteological characters and for apomorphic identifications of fossils. We investigate whether morphological features in the skulls of extant gerrhonotine lizards can be used to distinguish taxa at the species- and genus-level and assess whether newly discovered intra- and interspecific osteological variation alters the utility of previously reported apomorphic features. We examined skulls of species belonging to the gerrhonotine genera Elgaria and Gerrhonotus. These genera contain 17 extant species, but the cranial osteology of only a few species was previously examined. As a result, intra- and interspecific osteological variation of these gerrhonotines is poorly understood.
Methods
We employed high-resolution x-ray computed tomography (CT) to scan 25 alcohol-preserved specimens. We provide data on the skulls of all eight species of Elgaria, four for the first time, and five species of Gerrhonotus, three for the first time. We examined 3-D reconstructed skulls of the scanned specimens as well as dry, traditionally prepared skeletons (when they were available).
Results
We found that the purported diagnostic utility of many previously described morphological features is impacted because of substantial morphological variation between and within species. We present an assessment of osteological differences that may be useful to differentiate species of Elgaria and Gerrhonotus, many of which are present on isolated cranial elements commonly recovered as fossils, including the premaxilla, maxilla, parietal, pterygoid, prootic, dentary, and surangular. We demonstrate the importance of documenting patterns of osteological variation using large sample sizes, and the utility of examining disarticulated cranial elements of the squamate skull to identify diagnostic morphology. This study adds to a growing body of literature suggesting that extensive documentation of morphological variation is needed to further our understanding of the phylogenetic and diagnostic utility of morphological features across vertebrate clades. Efforts in that direction likely will benefit from examination of disarticulated skeletal elements.
... These newer systematic rearrangements indicate that more detailed studiesmostly combining morphological data-are needed to correctly assign leptotyphlopid species to genera. Data on skeletal morphology of different species of leptotyphlopids have been accumulated since the 19th century (e.g., Abdeen, Abo-Taira & Zaher, 1991a;Abdeen, Abo-Taira & Zaher, 1991b;Abdeen, Abo-Taira & Zaher, 1991c;Broadley & Broadley, 1999;Broadley & Wallach, 2007;Brock, 1932;Cundall & Irish, 2008;Duerden & Essex, 1923;Duméril & Bibron, 1844;Essex, 1927;Fabrezi, Marcus & Scrocchi, 1985;FitzSimons, 1962;Haas, 1930Haas, , 1931Haas, , 1959Hardaway & Williams, 1976;Kley, 2001Kley, , 2006List, 1966;McDowell & Bogert, 1954;Parker & Grandison, 1977;Pinto et al., 2015;Rieppel, 1979;Rieppel, Kley & Maisano, 2009). Broadley and Broadley (1999) studied southern African species of the subfamily Leptotyphlopinae, and found for the first time that the arrangement of the dorsal skull bones (e.g., paired or unpaired parietal; degree of separation in the midline in paired parietals; presence, position and shape of a postparietal bone) provides diagnostic characters that are useful for the differentiation of genera, and in some cases even species. ...
... Before this special issue, there were only rare exemplar studies of skulls of the subfamily Epictinae (e.g., Martins et al., 2021;Pinto et al., 2015), and only recently have skull characters been used for the first time to define a new genus (Habrophallos, see . According to the available information, the species and genera of Epictinae share a fused, unpaired parietal and differ from each other most conspicuously in having paired or unpaired supraoccipital and nasal bones (Broadley, 2004;Cundall & Irish, 2008;Curcio, 2003;Fabrezi et al., 1985;Haas, 1930;Kley, 2006;List, 1966;McDowell & Bogert, 1954;Pinto et al., 2015;Rieppel et al., 2009;Salazar-Valenzuela et al., 2015). ...
Since the rearrangement of all leptotyphlopid species previously known as “Leptotyphlops” in Adalsteinsson et al. (2009)'s paper, several taxa have remained untested regarding their generic identity and have been assigned to different genera based on phenotypic data or, in some cases, without any clear justification. Most of the difficulties in assigning some leptotyphlopid taxa are due to their conserved external morphology, summed with a relatively small number of available specimens, which complicate the recognition of a unique combination of characters for their reasonable generic allocation. On the other hand, recent osteological studies—especially those on the skull—provide relevant data combinations for species assignment and even for the recognition of new genera. In this work, we have attempted to determine the generic allocation of Epictia unicolor and Trilepida guayaquilensis—both species currently known only by their holotype—based on a detailed description of cranial and post‐cranial osteology. We confirm the assignment of E. unicolor to the genus Epictia despite the divergent configuration of cephalic shields. Based mainly on data from the skull, suspensorium, and cervical vertebrae but supported by external morphology as well as a redescription of the holotype, we propose the assignment of Trilepida guayaquilensis to the genus Epictia. This study provides not only detailed data on the osteology of Epictia, but also a first approach to the putative combination of osteological characters for the genus.
... Kuhn (1940b) established two large platynotan taxa from Geiseltal: Melanosauroides giganteus and Ophisauriscus eucarinatus. Melanosauroides giganteus was established upon a beautiful disarticulated skeleton with skull (GMH Ce III-4139-1933) which was later considered to have shinisaurian affi nities (McDowell & Bogert 1954). On the other hand, the holotype of Ophisauriscus eucarinatus, is a much more incomplete specimen, being solely a hind limb with osteoderms (GMH Ce IV-4021-1933). ...
... Th is has been repeatedly demonstrated particularly for anguines, in which the majority of fossil forms are well defi ned on the basis of their parietal features (Klembara 1979(Klembara , 1981(Klembara , 2012(Klembara , 2015Klembara & Green 2010;Klembara & Rummel 2018). Parietals have also been shown to possess unique diagnostic features for other anguimorphs, such as lanthanotids (McDowell & Bogert 1954), shinisaurians (e.g., Klembara 2008;Smith & Gauthier 2013), helodermatids (e.g., Hoff stetter 1957Augé 2005), and varanids (e.g., Ivanov et al. 2018). Th is taxonomic importance of parietals apparently applies also to the diverse Paleogene European platynotans. ...
A long-forgotten, old collection of lizards from the Phosphorites du Quercy in southern France, housed in the Naturhistorisches Museum in Vienna (NHMW), is described in detail in this paper. The material, consisting of several almost complete cranial and postcranial disarticulated elements, originates from different, imprecisely known localities. Nevertheless, the completeness and exceptional preservation of many of these specimens permitted the identification of new taxa, as well as the recognition
and better understanding of novel anatomical features of previously described forms. Among the specimens, the material described herein and referred to Cadurcogekko cf. piveteaui ranks among the most complete cranial remains of Paleogene gekkotans. A clarification about the type material of the previously described species Cadurcogekko verus Bolet, Daza, Augé & Bauer, 2015, is provided. A new species of lacertids is established, Pseudeumeces kyrillomethodicus n. sp. Additional, large lacertid
material is referred to Mediolacerta Augé, 2005, representing also the largest one attributable to this genus. At least two glyptosaurine taxa are present in this collection, among which, the genus Paraplacosauriops Augé & Sullivan, 2006, is represented by exceptional cranial material, referred to Paraplacosauriops quercyi (Filhol, 1882). The completeness of the cranial material of Paraplacosauriops permits a more comprehensive understanding of its maxillary and mandibular anatomy. A detailed
documentation of cranial and postcranial material for the genus Palaeovaranus Zittel, 1887-1890, is conducted. The new maxilla described herein allows a better understanding of the peculiar maxillary features of the genus Palaeovaranus. Emended diagnoses are provided for the genus Palaeovaranus and its type species Palaeovaranus cayluxi Zittel, 1887-1890. The parietal morphology of Palaeovaranus is analyzed in detail and intraspecific variation in this element is assessed. A new species of Palaeovaranus
is established, Palaeovaranus lismonimenos n. sp., on the basis of an almost complete parietal that can be differentiated from that of Palaeovaranus cayluxi on the basis of a number of distinctive features. Additional, previously published specimens from Quercy are here referred to Palaeovaranus lismonimenos n. sp., representing younger individuals of this species, and photographs of this material is provided for the first time. The diversity of platynotans in the Paleogene of Europe is discussed and their distinction on the basis of parietal morphology is provided. According to the new emended
diagnosis for Palaeovaranus, the genus Melanosauroides Kuhn, 1940, is revalidated herein to accommodate Melanosauroides giganteus Kuhn, 1940, from the late early or middle Eocene of Geiseltal, Germany. So far, Melanosauroides giganteus is solely known from its type area in Geiseltal, and all previously supposed occurrences of this taxon in Quercy are discarded. Abundant anguimorph vertebral material is referred to Placosaurus sp., Melanosaurini indet., Anguinae indet., Palaeovaranus sp., Saniwa sp., and Anguimorpha indet., although it is highlighted that certain of these referrals
should be taken into consideration with caution. Especially, the problem of certain large isolated lizard vertebrae from Quercy is addressed; a tentative, potential distinction between vertebrae of the genera Palaeovaranus and Placosaurus Gervais, 1848-1852, is suggested, although admittedly only articulated skeletons of these genera may confirm or refute such taxonomic referrals. The importance of fossil squamates from the area of the Phosphorites du Quercy is highlighted. Detailed figuring of the specimens is provided through the means of both photography and micro-CT scanning, with 3D models of the most significant material also presented. This is the first time that micro-CT scanning
is conducted on fossil squamates from Quercy. The many figures provided in this paper may serve as a pictorial key guide for fossil lizards from the Paleogene of Europe.
... However, Gilmore (1928) recognized these fossil lizards to be members of the extant lizard family Anguidae. Years later, McDowell and Bogert (1954) established and placed the North American fossil anguids in the extinct subfamily Glyptosaurinae within the family Anguidae. The family Placosauridae (Kuhn, 1940), although having taxonomic priority, has been considered synonymous with Glyptosauridae, and thus the Glyptosaurinae (see Estes, 1983a;McDowell and Bogert, 1954). ...
... Years later, McDowell and Bogert (1954) established and placed the North American fossil anguids in the extinct subfamily Glyptosaurinae within the family Anguidae. The family Placosauridae (Kuhn, 1940), although having taxonomic priority, has been considered synonymous with Glyptosauridae, and thus the Glyptosaurinae (see Estes, 1983a;McDowell and Bogert, 1954). Gilmore (1928) was the first to list the various species of Glyptosaurus in stratigraphic sequence and provided a taxonomic key to the species. ...
Glyptosaurine lizards (Glyptosaurinae, Anguidae) are an extinct group of heavily armored lizards known from North America, Europe and Asia. Glyptosaurine lizards, taxa that possess fully developed tuberculated dermal armor, appear to have been established in North America by late early Puercan time (To3). “Proxestops,” a taxon distinguished by a combination of vermiculate and tuberculated osteoderm sculpturing, is considered to be a non-glyptosaurine, a sister taxon of the Glyptosaurinae. Known from only fragmentary remains, its wide chronostratigraphic distribution suggests that “Proxestops” is a form genus that, in all probability, represents more than one taxon, that ranges from the middle Paleocene to the early Eocene of North America. Moreover, the taxa Odaxosaurus piger, Parodaxosaurus sanjuanensis and “Proxestops” are best considered “proto-glyptosaurines”. “Melanosaurins” and glyptosaurins were well-established by the early Eocene, especially in North America, and are here documented by their type species and chronostratigraphic levels. Both tribes are present in Europe (MP7), too, but the record is not as estensive as that of North America. The North American taxon Gaultia silvaticus (Wa0) is transitional between a “melanosaurin” and glyptosaurin. Because it lacks the well-defined hexagonal osteoderms that characterize the Glyptosaurini, it is removed from that group and considered to be a “melanosaurin”. The “melanosaurin” taxon “Xestops” savagei (Wa4–Wa6) cannot be referred to Xestops (Br2) based on non-corresponding elements and because superficial similarity does not justify assignment to this taxon. Arpadosaurus sepulchralis (Wa6?), whose holotype is a fragmentary right frontal, is considered a subjective junior synonym of A. gazinorum, based on minor differences in the epidermal scale pattern that probably represent individual variation. “Glyptosaurus” agmodon (Wa6?), based on a partial right maxilla, cannot be referred to Glyptosaurus (sensu stricto), and the material upon which this taxon is based bears strong resemblance to material identified as cf. “?Paraglyptosaurus” yatkolai (Wa5–Wa6). “Glyptosaurus” rhodinos (Wa5) is based on an incomplete parietal, and its reference to Glyptosaurus is considered problematic. Eoglyptosaurus donohoei (Wa7) is probably valid and is re-established here. Glyptosaurus (sensu stricto) is known solely from the middle Eocene (Br2) by G. sylvestris. Dimetoposaurus wyomingensis (Br3) is removed from Xestops vagans because its synonymy was based on superficial similarities. Helodermoides tuberculatus, the largest and last glyptosaurin (Ch3), is restricted to the Chadronian of North America. Only the “melanosaurin” Peltosaurus granulosus (Or2–Or3), which includes the species P. abbotti, seems to have crossed the Eocene-Oligocene boundary, and appears to be largely restricted to the Orellan, but extended into the Arikareean. European glyptosaurines are also represented by both glyptosaurins and “melanosaurins” early in the Eocene (MP7). Placosauriops-like “melanosaurins” are known from Dormaal (MP7), and the glyptosaurin taxon?Placosaurus ragei occurs at the same level. “Placosauriops abderhaldeni” has been identified from the Grube Messel (MP11), but this assignment remains dubious because the species has not been adequately diagnosed, and the holotype species is from the Geiseltal (MP13), which is some 4.5 million years younger. Placosauriops weigelti (MP13) is the only valid species of this genus. Paraxestops stehlini (MP14) is not referable to the North American taxon Xestops, and its relationship to Placosauriops has not been studied. The late Eocene glyptosaurins Placosaurus estesi (MP17) and P. rugosus (MP18) are the last glyptosaurines known from Europe and appear to have gone extinct at the Eocene-Oligocene boundary, casulties perhaps of the “Grande Coupure”. Asian glyptosaurines are known solely from one species, Stenoplacosaurus mongoliensis, from the middle Eocene (Sharamurunian) of China. Glyptosaurines most likely originated in North America, diversified by late Paleocene time, and rapidly spread across the North Atlantic into Europe by the early Eocene. Both “melanosaurins” and glyptosaurins took a foothold in Europe by the early Neustrian, but the glyptosaurins, aside from one occurrence (Dormaal, MP7), were conspicuously absent for most of Neustrian through early Robiacian time. In North America, glyptosaurins diversified during the early and middle Eocene, while in Europe small “melanosaurins” were a prominent part of the paleoherpetofauna, and glyptosaurins are unknown for most of the Neustrian through the Geiseltalian, in both the fossilferous Lagerstätten of Messel and Geiseltal. Stenoplacosaurus is the only known glyptosaurin glyptosaurine from Asia, and its abrupt appearance during the late Eocene suggests the possiblity of a Beringian dispersal from North America into Asia.
... At first glance, these extremely small snakes look more like worms than snakes. 'Scolecophidia' have long been considered lizards (BONAPARTE, 1839;GRAY, 1845) or a lineage of limbless lizards (MCDOWELL & BOGERT, 1954;ROBB, 1960) but, without any doubts, ophidian origin of 'scolecophidians' is generally accepted today (SZYNDLAR & GEORGALIS, 2023). ...
This article describes the first find of blind snake remains from the Middle Miocene sediments in the Vracevic locality (Western Serbia). The numerous snake remains were isolated from the fossil material of the Vracevic site. Among the many fragmented vertebrae, only one has been identified as belonging to a ?scolecophidian?. This vertebra is characterized by the neural arches depressed dorsoventrally; the vestigial neural spine limited to the most posterior part of a neural arch; posterodorsal lamina of neural arch slightly concave; paradiapophyses developed above the ventral margin of cotylar rim; indistinct haemal keel visible only on the anterior part of vertebra centrum.
... In addition to those listed in Institutional Abbreviations, the following abbreviations are Lanthanotus borneensis, scored from CT scans of (AMNH R-87375, AMNH R-113983, and UF Herp 16268), as well as the description by McDowell and Bogert (1954). Heloderma horridum, scored from firsthand observation of AMNH R-71664 and a CT scan of UF Herp 153328. ...
Mosasaurs are large, carnivorous aquatic lizards with a global distribution that lived during the Late Cretaceous. After 200 years of scientific study, new mosasaur species are still being discovered as new localities are explored and specimens collected long ago are reevaluated using modern standards of species delimitation. Even so, the phylogenetic positions of many key taxa are unresolved and therefore our understanding of mosasaur macroevolution is muddled. Here, we describe a new genus and species of mosasaurine mosasaur comprising a partial skull and skeleton from the Pembina Member of the Pierre Shale Formation in Cavalier County, North Dakota. The lower bound on the age of the specimen is 80.04 ±0.11 Ma, provided by the underlying bentonite bed. Its skull and jaws are nearly complete, and the postcranial skeleton preserves seven cervical vertebrae with three hypapophyseal peduncles, 11 ribs, and five anterior dorsal vertebrae. The new specimen was scored into a modified version of an existing phylogenetic matrix of Mosasauroidea and was recovered in a polytomy with Clidastes; however, given that its morphology is significantly different from that of Clidastes, we refer it to a new genus and species, Jormungandr walhallaensis. Notably, this new taxon shares a mosaic of features seen in both basal (e.g., Clidastes; high dental counts) and derived (e.g., Mosasaurus; subrectangular quadrate) mosasaurines, in addition to possessing its own unique suite of autapomorphies. Given that it possesses morphology intermediate between Clidastes and Plotosaurini, we suspect that future analyses of mosasaur phylogeny, following the addition of new characters and taxa, will recover Jormungandr as transitional between them. Its occurrence increases the known diversity of mosasaurs from the Pembina Member and is the earliest mosasaur to possess autapomorphies of Plotosaurini. Finally, we also analyzed the matrix using different outgroups to test their effect on tree topology and resolution, and found that including multiple nonmosasauroid anguimorphs increased resolution, but not support, of mosasaurid ingroup relationships.
... Furthermore, Rieppel et al. (2009) reports different degrees in ossification for the supratemporal in anomalepidids, ranging from the much reduced supratemporal of Typhlophis squamosus (Schlegel, 1839) to absent in Anomalepis aspinosus Taylor, 1939. Palci (2014 also reports a variable presence of supratemporal bones in the genus Anomalepis, that was previously reported as lacking a supratemporal bone (McDowell and Bogert, 1954;Haas, 1968;Rieppel et al., 2009). Rieppel (1979) suggests that neoteny, paedomorphosis in ontogenetic ossification, can be attributable for the disappearance of the lateral wing of the basisphenoid in Scolecophidia. ...
... The morphological specializations of the snake skeleton and the lack of early fossil representatives have hampered attempts to resolve the relationships of snakes to extant lizards. McDowell and Bogert [110] argued that snakes were related to anguimorphs, particularly varanids and/or lanthanotids, and several cladistic analyses (e.g., [115,116,123,124,129]) supported this (snake-mosasaurian relationships notwithstanding). However, convergence between snakes and other limbless squamates (e.g., amphisbaenians, dibamids, limbless scincids, and anguids) tends to confound analyses based solely on phenotypic data (e.g., [6,59,116,130]), leading to artificial groupings. ...
Snakes comprise nearly 4,000 extant species found on all major continents except Antarctica. Morphologically and ecologically diverse, they include burrowing, arboreal, and marine forms, feeding on prey ranging from insects to large mammals. Snakes are strikingly different from their closest lizard relatives, and their origins and early diversification have long challenged and enthused evolutionary biologists. The origin and early evolution of snakes is a broad, interdisciplinary topic for which experts in palaeontology, ecology, physiology, embryology, phylogenetics, and molecular biology have made important contributions. The last 25 years has seen a surge of interest, resulting partly from new fossil material, but also from new techniques in molecular and systematic biology. This volume summarises and discusses the state of our knowledge, approaches, data, and ongoing debates. It provides reviews, syntheses, new data and perspectives on a wide range of topics relevant to students and researchers in evolutionary biology, neontology, and palaeontology.
... In this view of squamates interrelationships, based on morphological data (e.g. McDowell and Bogert, 1954;Pregill et al., 1986;Caldwell, 1999;Conrad, 2008;Gauthier et al., 2012), helodermatids and varanids were closely related, and the term "Varanoidea" was used to group them as well as related extinct taxa. Gao and Norell (1998) used the term in a more restrictive sense, consisting in the most recent common ancestor of Telmasaurus and Varanidae, and all its descendants. ...
Appendicular remains of squamate reptiles are barely described in the fossil record due to their low preservational potential and generally poor diagnostic information. Not many squamate fossil individuals preserve appendicular bony elements, these being mainly restricted to the rare articulated specimens found in a limited number of localities with specific conditions that favor exceptional preservation. Detailed descriptions of these bones, especially tarsals and metatarsals, are thus scarce in the literature due to the lesser relevance given to these elements in most anatomical descriptions. In this study we analyze an unpublished fossil specimen from the Maastrichtian of Basturs-1 (Lleida, Catalonia, Spain) corresponding to several articulated appendicular pes bones of a possible member of Varaniformes. We also provide detailed insights on the anatomy of the tarsalia and metatarsalia, particularly in angui- morphs. The fossil specimen here described, with an estimated snout-vent length (SVL) of ~581 mm, reveals the putative varaniform from Basturs-1 as one of the largest Mesozoic terrestrial lizards, and possibly the largest from the European fossil record. Previous observations of an association between large lizards and dinosaur nesting sites are further supported by the find of this giant form in a locality known for the presence of numerous dinosaur eggs.
... This fossil specimen can be assigned to the "Anguimorpha" based on the following characters: a ventrally convex arch along the long axis; the presence of intramandibular septum; surangular and angular processes forming a notch (posterolateral dentary with surangular notch in Estes et al. [1988]); the assumption of the replacement teeth position (see above); infolded teeth-plicidentine (Estes et al., 1988;Evans, 2008;Conrad et al., 2011a). Moreover, traditionally, some features of the specimen (i.e., the absence of the subdental shelf [little developed in the examined specimen] and resorption pits in marginal teeth; the presence of the notch [not free, a weakly pointed eminence] in posteroventral corner of intramandibular septum; unicuspid, trenchant, recurved and widely spaced teeth) indicate the its allocation in "Varanoidea" (McDowell and Bogert, 1954;Pregill et al., 1986;Estes et al., 1988), but at least, Anguidae, Xenosauridae, and Shinisaurus crocodilurus can be excluded from candidates for the higher category accommodation of the present specimen because of the possession of the above-mentioned and the following additional features: absence of the free intramandibular septum; reduced tooth number [i.e., eleven], etc. (Estes, 1964;Estes et al., 1988;Bhullar and Smith, 2008;Evans, 2008). Also, the expanded tooth bases of the specimen show a wide, labially opening "U" in horizontal section as shared with many fossil Platynota, but not Varanus (Nydam, 2000;Bhullar and Smith, 2008). ...
A nearly complete left dentary of a lizard was excavated from the Lower Cretaceous Ohyamashimo Formation of the Sasayama Group in Tamba City, Hyogo Prefecture, Japan. The specimen shows several characters, which suggest its allocation in Monstersauria of the superfamily Varanoidea (Squamata: Anguimorpha). However, the specimen exhibits obvious differences from the known members of the whole Varanoidea. Thus, the specimen is described as a new taxon of cf. Monstersauria, Morohasaurus kamitakiens. This new species is characterized by a suit of unique features, such as the sinuous posteroventral rim of the dentary with a large U-shaped upper notch and small V-shaped lower notch, posteroventral corner of intramandibular septum with a weakly pointed eminence projecting posteriorly, and unicuspid, curved trenchant teeth with distinct blade-like carinae on their mesial and distal sides without grooves or serrations. Morohasaurus kamitakiensis might possibly be the oldest representative of the Monstersauria.
... Because of the limited nature of the fossil record, inferences on the evolutionary history of the scolecophidians depended upon analysis of patterns of biogeographic distribution of the extant taxa, and of their anatomical features including, to a limited extent, myology and other "soft" anatomical systems (Haas, 1930(Haas, , 1931(Haas, , 1962Martins, Silva, & Gonzalez, 2020;Mosauer, 1935;Robb, 1960;Robb & Smith, 1966), but more importantly their osteology, especially of the skull and mandible (Cundall & Irish, 2008;McDowell, 2008;McDowell Jr. & Bogert, 1954). Clear understanding of the three-dimensional architecture of the scolecophidian skull remained an elusive goal for nearly two centuries. ...
Scolecophidian snakes have long posed challenges for scholars interested in elucidating their anatomy. The importance, and relative paucity, of high‐quality anatomical data pertaining to scolecophidians was brought into sharp focus in the late 20th century as part of a controversy over the phylogeny and ecological origin of snakes. The basal position of scolecophidians in the phylogeny of snakes makes their anatomy, behavior, ecology, and evolution especially important for such considerations. The depauperate fossil record for the group meant that advances in understanding their evolutionary history were necessarily tied to biogeographic distributions and anatomical interpretations of extant taxa. Osteological data, especially data pertaining to the skull and mandible, assumed a dominant role in shaping historical and modern perspectives of the evolution of scolecophidians. Traditional approaches to the exploration of the anatomy of these snakes relied heavily upon serial‐sectioned specimens and cleared‐and‐stained specimens. The application of X‐ray computed tomography (CT) to the study of scolecophidians revolutionized our understanding of the osteology of the group, and now, via diffusible iodine‐based contrast‐enhanced computed tomography (diceCT), is yielding data sets on internal soft anatomical features as well. CT data sets replicate many aspects of traditional anatomical preparations, are readily shared with a global community of scholars, and now are available for unique holotype and other rare specimens. The increasing prevalence and relevance of CT data sets is a strong incentive for the establishment and maintenance of permanent repositories for digital data.
... Varanus; Erickson et al., 2003). ODs are common among scincids (Camp, 1923;Camaiti et al., 2019), gerrhosaurids (Camp, 1923;Nance, 2007), cordylids (Broeckhoven et al., 2015;Stanley, 2016;Broeckhoven, du Plessis & Hui, 2017b;Broeckhoven, De Kock & Le Fras Nortier Mouton, 2017a;Broeckhoven et al., 2018a), xenosaurids (Gao & Norell, 1998;Bhullar, 2011), helodermatids (Moss, 1969;Maisano et al., 2019;Kirby et al., 2020;Iacoviello et al., 2020), anguids (Hoffstetter, 1962;Strahm & Schwartz, 1977;Zylberberg & Castanet, 1985;Levrat-Calviac et al., 1986;Bochaton et al., 2015), anniellids (Bhullar & Bell, 2008), shinisaurids (Bever et al., 2005;Conrad et al., 2014), and lanthanotids (McDowell & Bogert, 1954;Maisano et al., 2002Maisano et al., , 2019. ODs are also found in some (but not all) species of varanids (Erickson et al., 2003;Maisano et al., 2019;Kirby et al., 2020) and lacertids (Estes et al., 1988;Borsuk-Białynicka et al., 1999;Constantini & Dell'Omo, 2010). ...
Osteoderms are mineralised structures consisting mainly of calcium phosphate and collagen. They form directly within the skin, with or without physical contact with the skeleton. Osteoderms, in some form, may be primitive for tetrapods as a whole, and are found in representatives of most major living lineages including turtles, crocodilians, lizards, armadillos, and some frogs, as well as extinct taxa ranging from early tetrapods to dinosaurs. However, their distribution in time and space raises questions about their evolution and homology in individual groups. Among lizards and their relatives, osteoderms may be completely absent; present only on the head or dorsum; or present all over the body in one of several arrangements, including non-overlapping mineralised clusters, a continuous covering of overlapping plates, or as spicular mineralisations that thicken with age. This diversity makes lizards an excellent focal group in which to study osteoderm structure, function, development and evolution. In the past, the focus of researchers was primarily on the histological structure and/or the gross anatomy of individual osteoderms in a limited sample of taxa. Those studies demonstrated that lizard osteoderms are sometimes two-layered structures, with a vitreous, avascular layer just below the epidermis and a deeper internal layer with abundant collagen within the deep dermis. However, there is considerable variation on this model, in terms of the arrangement of collagen fibres, presence of extra tissues, and/or a cancellous bone core bordered by cortices. Moreover, there is a lack of consensus on the contribution, if any, of osteoblasts in osteoderm development, despite research describing patterns of resorption and replacement that would suggest both osteoclast and osteoblast involvement. Key to this is information on development, but our understanding of the genetic and skeletogenic processes involved in osteoderm development and patterning remains minimal. The most common proposition for the presence of osteoderms is that they provide a protective armour. However, the large morphological and distributional diversity in lizard osteoderms raises the possibility that they may have other roles such as biomechanical reinforcement in response to ecological or functional constraints. If lizard osteoderms are primarily for defence, whether against predators or conspecifics, then this ‘bony armour’ might be predicted to have different structural and/or mechanical properties compared to other hard tissues (generally intended for support and locomotion). The cellular and biomineralisation mechanisms by which osteoderms are formed could also be different from those of other hard tissues, as reflected in their material composition and nanostructure. Material properties, especially the combination of malleability and resistance to impact, are of interest to the biomimetics and bioinspired material communities in the development of protective clothing and body armour. Currently, the literature on osteoderms is patchy and is distributed across a wide range of journals. Herein we present a synthesis of current knowledge on lizard osteoderm evolution and distribution, micro- and macrostructure, development, and function, with a view to stimulating further work.
... Furthermore, we found several specimens to have edentulous mandibles (a condition which Chretien et al., 2019 mistakenly generalized to all anomalepidids); among our examined specimens, teeth are only distinctly visible on specimens of Anomalepis mexicanus, Liotyphlops beui, and Typhlophis, though this may be an artifact of scan resolution. List (1966) and Haas (1964) found teeth on the dentary of Liotyphlops albirostris, Haas (1968) in Anomalepis aspinosus, and McDowell and Bogert (1954) in Helminthophis flavoterminatus and Typhlophis squamosus. As in other snakes, the interramal surface lacks articulatory or symphyseal facets (see also Kley, 2006). ...
Snakes—a subset of lizards—have traditionally been divided into two major groups based on feeding mechanics: “macrostomy,” involving the ingestion of proportionally large prey items; and “microstomy,” the lack of this ability. “Microstomy”—considered present in scolecophidian and early‐diverging alethinophidian snakes—is generally viewed as a symplesiomorphy shared with non‐snake lizards. However, this perspective of “microstomy” as plesiomorphic and morphologically homogenous fails to recognize the complexity of this condition and its evolution across “microstomatan” squamates. To challenge this problematic paradigm, we formalize a new framework for conceptualizing and testing the homology of overall character complexes, or “morphotypes,” which underlies our re‐assessment of “microstomy.” Using micro‐computed tomography (micro‐CT) scans, we analyze the morphology of the jaws and suspensorium across purported “microstomatan” squamates (scolecophidians, early‐diverging alethinophidians, and non‐snake lizards) and demonstrate that key components of the jaw complex are not homologous at the level of primary character state identity across these taxa. Therefore, rather than treating “microstomy” as a uniform condition, we instead propose that non‐snake lizards, early‐diverging alethinophidians, anomalepidids, leptotyphlopids, and typhlopoids each exhibit a unique and nonhomologous jaw morphotype: “minimal‐kinesis microstomy,” “snout‐shifting,” “axle‐brace maxillary raking,” “mandibular raking,” and “single‐axle maxillary raking,” respectively. The lack of synapomorphy among scolecophidians is inconsistent with the notion of scolecophidians representing an ancestral snake condition, and instead reflects a hypothesis of the independent evolution of fossoriality, miniaturization, and “microstomy” in each scolecophidian lineage. We ultimately emphasize that a rigorous approach to comparative anatomy is necessary in constructing evolutionary hypotheses that accurately reflect biological reality.
... Another of his early papers is an example of this almost preternatural skill. Along with the physiologist Charles Bogert he published on Lanthanotus (Bogert and McDowell 1954). At the time, this was a very rare animal, and only a handful of specimens were available among all the collections of the world. ...
... In 1899, Boulenger assigned L. borneensis to the Helodermatidae family, that includes the Gila monster, Heloderma suspectum, and the beaded lizard, H. horridum (Sprackland, 1999). Much later, based on anatomical characters, such as lack of grooved teeth and absence of a venom gland, McDowell and Bogert (1954) concluded that it should represent its own family, Lanthanotidae, as member of the Angiomorpha lineage. More recently, molecular genetic evidence confirmed its close relationship to monitor lizards (Varanidae) (Ast, 2001;Douglas et al., 2010;Wiens et al., 2012;Pyron et al., 2013). ...
Based on its mandibular gland secretion, the earless monitor lizard, Lanthanotus borneensis, has been considered a venomous animal like other members of the Toxicofera group, including Heloderma. In the present study, the gland structure and teeth of L. borneensis were examined by micro-tomography (μCT) and scanning electron microscopy (SEM), respectively, and proteomic analysis of the gland extract was performed. The mandibular gland consists of six compartments with separate ducts. The pleurodont teeth of the lower and upper jaw are not grooved but possess a sharp ridge on the anterior surface. Proteomic analysis of the gland extract confirmed previous studies that kallikrein enzymes are the major biologically active components. In view of the lizard's biology, its mandibular gland secretion is obviously not needed for prey capture or defence. It seems not justified the labelling of L. borneensis as a venomous animal. However, definitively answering this question requires toxinological studies on natural prey.
... Within Anguiformes, both concatenated and speciestree estimates support Shinisaurus as the sister taxon to varanids and Helodermatidae as the sister taxon to Anguioidea (Diploglossidae, Anniellidae, Anguidae, Xenosauridae). This topology conflicts with the one suggested by morphological data, including those with expanded fossil sampling, where helodermatids and Shinisaurus are traditionally recognized as the sister groups of varanids and Xenosaurus, respectively (McDowell and Bogert, 1954;Gao and Norell, 1998;Gauthier, 1998;Gauthier et al., 2012). However, Conrad (2008) has shown that Shinisaurus and Xenosaurus were not closely related, the former being the sister group of varanoids (including Helodermatidae) and the latter as the sister group of Anguidae (Conrad, 2008). ...
Genomics is narrowing uncertainty in the phylogenetic structure for many amniote groups. For one of the most diverse and species-rich groups, the squamate reptiles (lizards and snakes, amphisbaenians), an inverse correlation between the number of taxa and loci sampled still persists across all publications using DNA sequence data and reaching a consensus on the relationships among them has been highly problematic. Here, we use high-throughput sequence data from 289 samples covering 75 families of squamates to address phylogenetic affinities, estimate divergence times, and characterize residual topological uncertainty in the presence of genome scale data. Importantly, we address genomic support for the traditional taxonomic groupings Scleroglossa and Macrostomata using novel machine-learning techniques. We interrogate genes using various metrics inherent to these loci, including parsimony-informative sites, phylogenetic informativeness, length, gaps, number of substitutions, and site concordance to understand why certain loci fail to find previously well-supported molecular clades and how they fail to support species-tree estimates. We show that both incomplete lineage sorting and poor gene-tree estimation (due to a few undesirable gene properties, such as an insufficient number of parsimony informative sites), may account for most gene and species-tree discordance. We find overwhelming signal for Toxicofera, and also show that none of the loci included in this study supports Scleroglossa or Macrostomata. We comment on the origins and diversification of Squamata throughout the Mesozoic and underscore remaining uncertainties that persist in both deeper parts of the tree (e.g., relationships between Dibamia, Gekkota, and remaining squamates; and between the three toxiferan clades Iguania, Serpentes, and Anguiformes) and within specific clades (e.g., affinities among gekkotan, pleurodont iguanians, and colubroid families).
... Nopcsa (1908Nopcsa ( , 1923 was the first to propose that dolichosaurs were more closely related to snakes than to other Cretaceous aquatic squamates (the mosasaurs and aigialosaurs). From the start, this hypothesis was contentious, supported by some (e.g., McDowell and Bogert, 1954) but rejected by others (e.g., Féjérváry, 1918;Camp, 1923). The advent of computer generated cladistic analyses in the 1980's intensified the debate on the relationship of snakes and dolichosaurs. ...
Non-ophidian ophidiomorphs, colloquially referred to as ‘dolichosaurs,’ are small-bodied aquatic lizards that lived in shallow seaways, rivers, and reef environments during the Late Cretaceous. Preservational, geographic, and taphonomic biases in this group make trends in biodiversity difficult to assess. This is exemplified by the fact that the majority of the described species are monotypic and known only from single specimens, imparting very little information on morphological or spatial variation. Here we present a revision of the spatial and temporal distributions of non-ophidian ophidiomorph lizards (‘dolichosaurs’) from Cretaceous sediments worldwide. The fossil record of dolichosaurs begins in the Valanginian (Early Cretaceous). The late Early Cretaceous records are sparse but suggest a wide geographic distribution spanning the Tethys and Western Pacific. This is followed by a dense Cenomanian record from Tethyan and British deposits, and rarer specimens from North America. Though there is a substantial drop in the number of specimens recorded from the Turonian–Maastrichtian, these rare occurrences represent the largest geographical distribution of dolichosaurs: spanning Europe, North America, and South America before going extinct during the end-Cretaceous mass extinction. These occurrences indicate that ophidiomorphs most likely originated in the Jurassic Tethys and continued to radiate spatially and phylogenetically until the end of the Mesozoic, showing much more temporally and environmentally diverse patterns than previously indicated.
... This drove earlier views about digital evolution in the Gekkota as it presupposed that the ancestor of living geckos was padless and that pads evolved either at the ancestor of all non-eublepharids (Underwood 1954) or perhaps separately in diplodactylids and all other geckos (Moffat 1973;Russell 1979). Although McDowell and Bogert (1954) first included pygopodids within the Gekkota, Kluge (1987) recognized that the flap-footed lizards were embedded within the clade and considered them to be sister to the Diplodactylinae. This grouping made biogeographic sense, but a more fully resolved and supported set of relationships among the limbless pygopods, the padless Carphodactylini and toepad-bearing Diplodactylini would have consequences for the distribution of adhesive mechanism gains versus losses across the tree. ...
An evolutionary perspective on gecko adhesion was previously hampered by a lack of an explicit phylogeny for the group and of robust comparative methods to study trait evolution, an underappreciation for the taxonomic and structural diversity of geckos, and a dearth of fossil evidence bearing directly on the origin of the scansorial apparatus. With a multigene dataset as the basis for a comprehensive gekkotan phylogeny, model-based methods have recently been employed to estimate the number of unique derivations of the adhesive system and its role in lineage diversification. Evidence points to a single basal origin of the spinulate oberhautchen layer of the epidermis, which is a necessary precursor for the subsequent elaboration of a functional adhesive mechanism in geckos. However, multiple gains and losses are implicated for the elaborated setae that are necessary for adhesion via van der Waals forces. The well-supported phylogeny of gekkotans has demonstrated that convergence and parallelism in digital design are even more prevalent than previously believed. It also permits the reexamination of previously collected morphological data in an explicitly evolutionary context. Both time-calibrated trees and recently discovered amber fossils that preserve gecko toepads suggest that a fully-functional adhesive apparatus was not only present, but also represented by diverse architectures, by the mid-Cretaceous. Further characterization and phylogenetically-informed analyses of the other components of the adhesive system (muscles, tendons, blood sinuses, etc.) will permit a more comprehensive reconstruction of the evolutionary pathway(s) by which geckos have achieved their structural and taxonomic diversity. A phylogenetic perspective can meaningfully inform functional and performance studies of gecko adhesion and locomotion and can contribute to advances in bioinspired materials.
... The occurrence of osteoderms in varanids was mentioned previously only in passing. The fact that osteoderms, when present, are isolated both from each other and from the underlying cranial bones was reported by McDowell and Bogert (1954). Osteoderms were reported to be present in Varanus bengalensis, Varanus exanthematicus, Varanus giganteus, Varanus gouldii, Varanus salvator, and Varanus varius (Auffenberg, 1981;de Buffrénil et al., 2010;Erickson et al., 2003;Smith, 1935), but not in the young of those species (Auffenberg, 1981;Smith, 1935). ...
Osteoderms constitute a morphological system that plays an important role in squamate systematics. However, their study and visualization have always been difficult due to their isolated occurrence in the skin, among the first organs to be removed during the skeletonization process. High‐resolution X‐ray computed tomography (HRXCT) offers a nondestructive means of visualizing osteoderms both in their natural relationship to each other and to the underlying cranial bones. Although it is often stated that Varanus komodoensis has a “chain mail” of osteoderms, this morphological system was never described in this taxon. Further, given its size, it might be expected that V. komodoensis would present the extreme of osteoderm development in extant varanids, a group that tends to have weakly developed osteoderms or none at all. Indeed, our HRXCT scan of a 19‐year‐old captive individual reveals an elaborate mesh of cephalic osteoderms that are incredibly numerous and morphologically diverse. We describe this skeletal system and compare it to the cephalic osteoderms in other varanoids. Anat Rec, 302:1675–1680, 2019. © 2019 American Association for Anatomy
Osteoderms, bone plates in the skin, are widely but discontinuously distributed across the phylogeny of tetrapods. This and their pronounced morphological disparity has inspired many hypotheses on possible osteoderm functions. Most of these have not been systematically studied or summarised based on the published disparate literature. We provide here a comprehensive overview of the current state of knowledge in this field with a focus on extant non‐avian reptiles. We also discuss functions in other extant osteoderm‐bearing taxa and those inferred from the fossil record. The hypotheses are categorised into protection, lifestyle and locomotion, physiology, and visual functions. A comprehensive overview of future directions in this field is provided. With this review, we hope to encourage future research to investigate the functional aspect of osteoderms. This might inspire biomimetics and shed light on the role that osteoderm expression may have played in shaping present‐day biodiversity.
We here present a thorough documentation of the vertebral morphology and intracolumnar variation across non-caenophidian
snakes. Our studied sample of multiple individuals covers a large number of genera (67) and species (120), pertaining to almost all
extant non-caenophidian families. Detailed figuring of multiple vertebrae across the trunk, cloacal, and caudal series for many different individuals / taxa documents the intracolumnar, intraspecific, and interspecific variation. An emphasis is given in the trunk-tocaudal transition and the pattern of the subcentral structures in that region of the column. Extant non-caenophidian snakes show an astonishing diversity of vertebral morphologies. Diagnostic vertebral features for extant families and many genera are given, though admittedly vertebral distinction among genera in certain groups remains a difficult task. A massive compilation of vertebral counts for 270 species, pertaining to 78 different genera (i.e., almost all known valid genera) and encompassing all extant non-caenophidian families, is provided based on our observations as well as an extensive literature overview. More particularly, for many taxa, detailed vertebral counts are explicitly given for the trunk, cloacal, and caudal portions of the column. Extant non-caenophidian snakes witness an extremely wide range of counts of vertebrae, ranging from 115 up to 546. A discussion on the diagnostic taxonomic utility and potential phylogenetic value of certain vertebral structures is provided. Comparisons of the subcentral structures of the cloacal and caudal vertebral series are also made with caenophidian lineages. We anticipate that this illustrative guide will set the stage for more vertebral descriptions in herpetological works but will also be of significant aid for taxonomic identifications in ophidian palaeontology and archaeozoology.
Fossil identification practices have a profound effect on our interpretation of the past because these identifications form the basis for downstream analyses. Therefore, well-supported fossil identifications are paramount for examining the impact of past environmental changes on populations and communities. Here we apply an apomorphic identification framework in a case study identifying fossil lizard remains from Hall’s Cave, a late Quaternary fossil site located in Central Texas, USA. We present images and descriptions of a broad comparative sample of North American lizard cranial elements and compile new and previously reported apomorphic characters for identifying fossil lizards. Our fossil identifications from Hall’s Cave resulted in a minimum of 11 lizard taxa, including five lizard taxa previously unknown from the site. Most of the identified fossil lizard taxa inhabit the area around Hall’s Cave today, but we reinforce the presence of an extirpated species complex of horned lizard. A main goal of this work is to establish a procedure for making well-supported fossil lizard identifications across North America. The data from this study will assist researchers endeavoring to identify fossil lizards, increasing the potential for novel discoveries related to North American lizards and facilitating more holistic views of ancient faunal assemblages.
Whether snakes evolved their elongated, limbless bodies or their specialized skulls and teeth first is a central question in squamate evolution. Identifying features shared between extant and fossil snakes is therefore key to unraveling the early evolution of this iconic reptile group. One promising candidate is their unusual mode of tooth replacement, whereby teeth are replaced without signs of external tooth resorption. We reveal through histological analysis that the lack of resorption pits in snakes is due to the unusual action of odontoclasts, which resorb dentine from within the pulp of the tooth. Internal tooth resorption is widespread in extant snakes, differs from replacement in other reptiles, and is even detectable via non-destructive μCT scanning, providing a method for identifying fossil snakes. We then detected internal tooth resorption in the fossil snake Yurlunggur, and one of the oldest snake fossils, Portugalophis, suggesting that it is one of the earliest innovations in Pan-Serpentes, likely preceding limb loss. Living snakes replace their teeth without external resorption. Here, the authors use histology to show that odontoclasts resorb dentine internally and investigate this mechanism in fossil snakes.
Snakes comprise nearly 4,000 extant species found on all major continents except Antarctica. Morphologically and ecologically diverse, they include burrowing, arboreal, and marine forms, feeding on prey ranging from insects to large mammals. Snakes are strikingly different from their closest lizard relatives, and their origins and early diversification have long challenged and enthused evolutionary biologists. The origin and early evolution of snakes is a broad, interdisciplinary topic for which experts in palaeontology, ecology, physiology, embryology, phylogenetics, and molecular biology have made important contributions. The last 25 years has seen a surge of interest, resulting partly from new fossil material, but also from new techniques in molecular and systematic biology. This volume summarises and discusses the state of our knowledge, approaches, data, and ongoing debates. It provides reviews, syntheses, new data and perspectives on a wide range of topics relevant to students and researchers in evolutionary biology, neontology, and palaeontology.
Snakes comprise nearly 4,000 extant species found on all major continents except Antarctica. Morphologically and ecologically diverse, they include burrowing, arboreal, and marine forms, feeding on prey ranging from insects to large mammals. Snakes are strikingly different from their closest lizard relatives, and their origins and early diversification have long challenged and enthused evolutionary biologists. The origin and early evolution of snakes is a broad, interdisciplinary topic for which experts in palaeontology, ecology, physiology, embryology, phylogenetics, and molecular biology have made important contributions. The last 25 years has seen a surge of interest, resulting partly from new fossil material, but also from new techniques in molecular and systematic biology. This volume summarises and discusses the state of our knowledge, approaches, data, and ongoing debates. It provides reviews, syntheses, new data and perspectives on a wide range of topics relevant to students and researchers in evolutionary biology, neontology, and palaeontology.
Snakes comprise nearly 4,000 extant species found on all major continents except Antarctica. Morphologically and ecologically diverse, they include burrowing, arboreal, and marine forms, feeding on prey ranging from insects to large mammals. Snakes are strikingly different from their closest lizard relatives, and their origins and early diversification have long challenged and enthused evolutionary biologists. The origin and early evolution of snakes is a broad, interdisciplinary topic for which experts in palaeontology, ecology, physiology, embryology, phylogenetics, and molecular biology have made important contributions. The last 25 years has seen a surge of interest, resulting partly from new fossil material, but also from new techniques in molecular and systematic biology. This volume summarises and discusses the state of our knowledge, approaches, data, and ongoing debates. It provides reviews, syntheses, new data and perspectives on a wide range of topics relevant to students and researchers in evolutionary biology, neontology, and palaeontology.
Snakes comprise nearly 4,000 extant species found on all major continents except Antarctica. Morphologically and ecologically diverse, they include burrowing, arboreal, and marine forms, feeding on prey ranging from insects to large mammals. Snakes are strikingly different from their closest lizard relatives, and their origins and early diversification have long challenged and enthused evolutionary biologists. The origin and early evolution of snakes is a broad, interdisciplinary topic for which experts in palaeontology, ecology, physiology, embryology, phylogenetics, and molecular biology have made important contributions. The last 25 years has seen a surge of interest, resulting partly from new fossil material, but also from new techniques in molecular and systematic biology. This volume summarises and discusses the state of our knowledge, approaches, data, and ongoing debates. It provides reviews, syntheses, new data and perspectives on a wide range of topics relevant to students and researchers in evolutionary biology, neontology, and palaeontology.
Snakes comprise nearly 4,000 extant species found on all major continents except Antarctica. Morphologically and ecologically diverse, they include burrowing, arboreal, and marine forms, feeding on prey ranging from insects to large mammals. Snakes are strikingly different from their closest lizard relatives, and their origins and early diversification have long challenged and enthused evolutionary biologists. The origin and early evolution of snakes is a broad, interdisciplinary topic for which experts in palaeontology, ecology, physiology, embryology, phylogenetics, and molecular biology have made important contributions. The last 25 years has seen a surge of interest, resulting partly from new fossil material, but also from new techniques in molecular and systematic biology. This volume summarises and discusses the state of our knowledge, approaches, data, and ongoing debates. It provides reviews, syntheses, new data and perspectives on a wide range of topics relevant to students and researchers in evolutionary biology, neontology, and palaeontology.
IUCn Red List assessment
The Hampshire Basin, Southern England, contains three geological Formations, known as the 'Solent Group' (Headon Hill Formation, Bembridge Limestone Formation, Bouldnor Formation), spanning the Upper Eocene to the early Lower Oligocene. These sites are known for their diverse mammal assemblages, permitting detailed palaeoenvironmental analyses and investigations of migration and evolution patterns of mammals across Europe in the Palaeogene. This thesis focuses on the fossil lizard assemblages from the Solent group, describing the taxa present, cataloguing changes through time, and attempting to correlate patterns of change with the changing palaeoenvironment. Information from late Middle Eocene (Creechbarrow Limestone Formation; Barton Clay Formation) lizard assemblages has also been included. The 'Grande Coupure', an event notable for an overturn in the mammal assemblage of Europe, occurs near the end of Solent Group deposition. A number of mammal families (seven), which were previously unknown in Continental Europe, appear in the Hampshire Basin. At the same time, the Continental European lizard assemblage saw a reduction in diversity, and subsequent diversity has remained low. The lizard assemblage of the Hampshire Basin is compared to those of Continental Europe in terms of diversity and structure. Many families are found in common, although differences occur at a generic level. The horizons in the Hampshire Basin vary in the quality, quantity and diversity of lizard material present. The reasons for these differences are discussed and appear to be due to a combination of characters aside from the life-assemblage, including taphonomy and preservation. These may account for the apparent fall in diversity which occurs in the lizards throughout the Hampshire Basin sequence. Despite the difficulty of observing changes linked to the 'Grande Coupure', the lizard fossils of the Hampshire Basin Solent Group provide an important addition to our knowledge of squamates at the beginning of the Tertiary.
ABSTRAK. Biawak Kalimantan, Lanthanotus borneensis adalah jenis kadal yang dilindungi di Indonesia. Minat di luar negeri akan jenis endemik Borneo ini sebagai komoditas perdagangan maupun subyek penelitian cukup tinggi, sementara data populasinya di alam masih terbatas. Oleh karena itu, kami melakukan telaah populasi di habitatnya dan penelitian lanjutan untuk menunjang pengelolaan dalam rangka pemanfaatannya. Survei habitat dan populasi dilakukan di Kabupaten Landak, Provinsi Kalimantan Barat pada bulan Juni 2017 dan Juli 2018 dengan cara pengamatan langsung di lokasi dan wawancara dengan pihak-pihak terkait tentang keberadaan dan potensi perdagangannya di lokasi survei. Penelitian lanjutan tentang pilihan pakan berdasarkan mangsa alaminya dilakukan di Museum Zoologicum Bogoriense (MZB) di Kabupaten Bogor, Provinsi Jawa Barat dengan metode focal animal sampling dan analisis preferensi Neu. Penelitian kandungan nutrisi pakan terpilih juga dilakukan di MZB dengan metode proksimat untuk mengetahui kandungan protein kasar, lemak kasar, abu dan energi total. Kami menduga populasi Biawak Kalimantan berada di lokasi survei di sekitar Desa Semunti dan di kaki Gunung Nyiut, meskipun kami tidak menjumpai kadal ini selama periode survei. Karakteristik hutan tropis dengan aliran sungai kecil berair jernih dengan substrat lumpur berpasir di dasarnya mengindikasikan kesesuaian habitat dan ketersediaan mangsanya. Hasil uji pilihan pakan dan kandungan nutrisinya mengindikasikan sifat karnivora jenis kadal ini yang diduga memangsa hewan-hewan invertebrata berukuran kecil. Di dalam kandang, kadal ini mengkonsumsi pakan dengan kadar lemak dan protein yang relatif tinggi, misalnya cacing tanah dan daging udang. Hasil penelitian ini berguna untuk menunjang pengelolaan populasi Biawak Kalimantan di habitatnya (in-situ) maupun di luar habitatnya (ex-situ).
ABSTRACT. Biawak Kalimantan, Lanthanotus borneensis is a protected species of lizard in Indonesia. While wild population data still remain scarce, demands on this Borneo endemic for international trade is relatively high, as are interests on the species for scientific research. Thus, we planned a study on wild populations and habitats, as well as two further studies to provide data for management and utilization purposes. Field surveys were conducted in Landak, West Kalimantan in
Armored skin resulting from the presence of bony dermal structures, osteoderms, is an exceptional phenotype in gekkotans (geckos and flap‐footed lizards) only known to occur in three genera: Geckolepis, Gekko, and Tarentola. The Tokay gecko (Gekko gecko LINNAEUS 1758) is among the best‐studied geckos due to its large size and wide range of occurrence, and although cranial dermal bone development has previously been investigated, details of osteoderm development along a size gradient remain less well‐known. Likewise, a comparative survey of additional species within the broader Gekko clade to determine the uniqueness of this trait has not yet been completed. Here, we studied a large sample of gekkotans (38 spp.), including 18 specimens of G. gecko, using X‐rays and high‐resolution computed tomography for visualizing and quantifying the dermal armor in situ. Results from this survey confirm the presence of osteoderms in a second species within this genus, Gekko reevesii GRAY 1831, which exhibits discordance in timing and pattern of osteoderm development when compared with its sister taxon, G. gecko. We discuss the developmental sequence of osteoderms in these two species and explore in detail the formation and functionality of these enigmatic dermal ossifications. Finally, we conducted a comparative analysis of endolymphatic sacs in a wide array of gekkotans to explore previous ideas regarding the role of osteoderms as calcium reservoirs. We found that G. gecko and other gecko species with osteoderms have highly enlarged endolymphatic sacs relative to their body size, when compared to species without osteoderms, which implies that these membranous structures might fulfill a major role of calcium storage even in species with osteoderms. Distribution of osteoderms in the skull of a large sized Tokay gecko (Gekko gecko).
As windows into the deep history of neuroanatomy, endocasts may provide information about the central nervous system of fossil taxa. Based on exceptionally preserved specimens of coeval mosasauroids (Squamata) and plesiosaurians (Sauropterygia), from the Turonian outcrops of Goulmima (Southern Morocco), the aim of this work was to describe for the first time in detail the endocranial anatomy of these two major clades of Mesozoic marine reptiles to provide insights about their sensory abilities, and thus to understand their cohabitation, interactions and niche partitioning. The endocranial anatomy of related extant squamates, mainly snakes but also varanids and amphisbaenians, also almost unknown until now, has been performed for the first time and used for comparative purpose to analyze the form-function relationships associated to endocasts. The analysis of the endocranial variability in extant squamates pointed out that endocasts reflect both phylogenetic and ecological signals, and that the relative size of each endocranial structure can be used to reveal differences in vision and olfaction according to taxa. Among fossil taxa, computed tomography was used to reconstruct in detail the cranial morphology of three unpublished specimens of Plesiosauria. These specimens have been examined and described, two have been referred to the elasmosaurid Libonectes morgani and the third one is an indeterminate polycotylid. The 3D morphology of the endocast has been reconstructed for these plesiosaurian specimens and the basal mosasauroid Tethysaurus nopcsai. The results show that the endocranial morphology of Plesiosauria differs from that know in other extinct and extant vertebrates. Based on the relative size of the structures composing their endocasts, both the mosasauroid Tethysaurus and the plesiosaurians seem to rely more on vision than on olfaction to interact with their environment. However, these new endocast data, added to information already available in the literature suggest different modes of locomotion and hunting techniques, which probably allowed them to coexist in Goulmima as quaternary consumers.
Glyptosaurinae is an extinct group of anguid lizards commonly found in the Cretaceous and Paleogene fossil record of North America and Eurasia. Glyptosaurines are well documented up until the middle Oligocene, but the temporal extent of the group was never constrained precisely. Here, I document the youngest known record of glyptosaurine lizards. I describe 10 fossils of the glyptosaurine Peltosaurus granulosus from the Monroe Creek and upper Sharps formations of Sharps Corner, South Dakota. The youngest known occurrence of Peltosaurus and Glyptosaurinae is between 27.4 and 26.4 Ma, based on a correlation of the magnetozone of the Monroe Creek Formation with chron C9n. Those dates are in the age range of a hypothesized middle–late Oligocene warming event. I review relevant morphological characteristics previously described for Peltosaurus and provide images of the holotypes of Peltosaurus abbotti and Peltosaurus granulosus, as well as two relatively complete specimens of Peltosaurus granulosus. I also establish an apomorphy of Peltosaurus on the frontal bone. Additionally, I correct an error in the literature pertaining to the original description of Peltosaurus.
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